B-36 Peacemaker - Design
The beginning of work on the "B-36 super bomber" can be attributed to the first months of 1941. The United States was still in a state of neutrality, though actively supporting Britain with military supplies. Development of a long range bomber was spurred by Nazi Germany's spectacular campaigns at the outset of World War II. It took Hitler just 20 days to crush the Polish army in September 1939 and but a few weeks for the German forces to speed across the Low Countries and France in 1940. (The western campaign started on 10 May; the French surrendered on 22 June).
Even though the scheduled invasion of the British Isles had been postponed, they seemed far from secure in the fall of 1940. The loss of Britain would leave the United States without European allies and with no bases outside the Western Hemisphere. This last stronghold of freedom in Europe, which, after surviving the Dunkirk tragedy and showing iron stamina during the Battle of Britain, continued to confront the Nazi monster, which had swallowed in a year and a half almost all the good old respectable Europe and was preparing to strike at the USSR, and then in the shortest possible time to get rid of obstinant British. In the Pacific, the dynamic Japanese empire, the Far Eastern ally of the Third Reich, was increasingly resolving its claims to hegemony in this region.
In the United States, it was understood that the entry into the World War for the country was a matter of the near future, and that with the darkest prospects: the defeat of Britain, the defeat of Russia or its final alliance with the Nazis and Japanese expansion - would put the United States in a position of a lonely warring fortress, remote from its enemies in thousands of miles of ocean open spaces. The early successes of the German offensive against Russia in June 1941 further deepened America's concern.
With such a possible geopolitical and military-strategic layout for the defense of the country and an attack on the aggressors, the country was vitally needed powerful naval forces and strategic air force equipped with aircraft capable of delivering crushing blows to the metropolitan territory of the enemy and its allies. The United States had a powerful fleet, it was necessary to create strategic aviation, and first of all to design and build a giant bomber aircraft capable of dropping bombs on Germany or Japan after take-off from bases in the United States and returning back.
The Army Air Corps (the Army Air Forces was not formally established until 20 June 1941) therefore needed a long range bomber that could carry the war to any enemy from the American continent.
When creating the aircraft, the greatest attention was paid to the achievement of intercontinental flight range. The designers were well aware that the flight range is proportional to the aerodynamic quality of the bomber, the relative mass of its fuel and inversely proportional to its specific consumption. In order to maximize the aerodynamic quality of the B-36 Peacemaker future strategic bomber, it was decided to use a large elongation wing with laminar profiles. To reduce the level of drag, the engines were decided to install inside the wing and apply the pushing screws. The smooth surface of the fuselage of the bomber was also not broken by any protruding detail; the cockpit of pilots entered into his circuit, and all defensive installations with coupled automatic 20-mm guns were decided to be made retractable.
The main requirement of the military was the range of flight without refueling, which was supposed to be at least 16,093 km, in addition, it was necessary to provide a speed of flight within 386-483 km / h and a practical ceiling of not less than 10 670 meters. Of the four proposed aircraft designs, the US military opted for the Model 36, which featured a sealed fuselage and a 1.83-meter-long root wing, which provided access to a powerplant that consisted of six reciprocating piston engines with propellers during flight.
To improve the weightiness of the bomber, the most modern high-strength aluminum alloys of 75ST were used very widely at that time, and the AN-M-29 magnesium alloys were used in the less critical units. Among other things, about half of the fuselage was made of magnesium alloy, for this reason one of the unofficial nicknames of the future B-36 bomber was the "Magnesium Monster". The total mass of magnesium parts was up to 10% of the total mass of the airframe. At the same time, the entire fuel stock was located in the winged compartments. The bomber's wing, whose deflection under the load reached two meters, the designers calculated as a dynamically elastic design, which at that time was an innovation.
In addition to the intercontinental flight range, another rather difficult task for the US military was a huge bomb load. When the technical requirements for the bomber were only developed, it was still more than one year before the start of the famous Manhattan project, and it was possible to increase the strike power of the aircraft so that it was able to solve strategic tasks only at the expense of the possibility of taking a large number of ordinary bombs on board. In order to place the assigned 32 660 kg of bombs, the designers had to design a bomb compartment with a length of more than 20 meters and a diameter of about 3 meters. Such a bomb detonation determined other dimensions of the aircraft, in particular, its famous wing span of 70 meters.
The rather long bomb bay forced to expand the range of permissible centerings. For this purpose, the wing of the aircraft was given a small sweep. At that, the total volume of the bomb compartment, which was conditionally divided into 4 sections, was 68% of the total volume of the bomber fuselage. The very large cut-outs for the bombardists forced the designers to partially abandon the semi-monocoque design of the fuselage that was generally accepted in those years. The middle part of the fuselage, located between the two hermetic cabins, was a truss structure with light magnesium sheathing. The large dimensions of the aircraft and, consequently, the very large take-off mass, exceeding 140 tons, required the designers to use the six most powerful engines at that time - 28-cylinder four-row Pratt & Whitney R-4360-25 air cooling.
Initially, the Convair B-36 bombers were intended exclusively for "carpet" bombardments using conventional high-explosive and incendiary bombs. For this, the aircraft received a huge bomb-bay, conditionally divided into parts. Two compartments were located in front of the wing, and two behind it. In addition, special racks with locks were installed on the main fuselage farms, on which, if necessary, it was possible to mount different models of bomb racks. At the top of the bomb compartment there were power jumpers, which allowed to fasten blocks and hoists for suspension of heavy ammunition.
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